1. Field of the Invention
The present invention relates to an inspecting method and an inspecting apparatus for a liquid crystal display panel, for inspecting non-uniformity of a gap between two glass plates that hold a liquid crystal of a liquid crystal display panel.
2. Description of the Related Art
At first, an example of a structure of an LCD (liquid crystal display) panel will be briefly explained below with reference to FIG. 1.
As shown in FIG. 1, an LCD panel 1 has a liquid crystal material 3 sealed between two glass plates 2a and 2b, and has spacers 4 inserted in the liquid crystal material 3 so as to make a gap between the two glass plates 2a and 2b in which the liquid crystal material 3 is sealed uniform.
Further, between the glass plates 2a and 2b, there are also provided orientation films 5a and 5b, transparent electrodes 6a and 6b, a switching element 7 and an RGB color filter 8. The inside of the two glass plates 2a and 2b is sealed at their both outer peripheries with a sealing material 9. The LCD panel 1 is further provided with polarization plates 10a and 10b, a driving IC 11 and a back-light 12.
In the process of manufacturing this LCD panel 1, there arises a case where a gap between the two glass plates 2a and 2b becomes not uniform when the liquid crystal material 3 is charged into this gap.
As a conventional inspecting method for inspecting a gap between the two glass plates 2a and 2b in a manufacturing line of this LCD panel 1, there has been employed a method comprising the steps, for example, of: illuminating the LCD panel 1 to be inspected with a sodium lamp or the like; counting the number of Newton rings appearing on the LCD panel 1 by visual observation; and deciding a level of uniformity based on the number of Newton rings, whereby to decide on a pass or a failure of the LCD panel.
According to this inspecting method, in order to decide a level of uniformity of the gap between the two glass plates 2a and 2b of this LCD panel, the center part of Newton rings is pressed by a projected object. When the inside liquid crystal tends to spread out by this pressing, a decision is made that the panel surface is convex. When the inside liquid crystal tends to gather together, a decision is made that the panel surface is concave. This conventional inspecting method has not be convenient in that it is necessary to press the surface of the liquid crystal display panel with this projected object.
As another inspecting method, there is a method of inspection by pin-pointing the gap with an interference membrane thickness gauge or the like. For carrying out the inspection by this method, it is necessary to inspect a large number of points. Therefore, this method has been inconvenient in that it takes a long time for inspecting each one liquid crystal display panel.